scholarly journals Statistical Relationship between Interplanetary Magnetic Field Conditions and the Helicity Sign of Flux Transfer Event Flux Ropes

2021 ◽  
Author(s):  
R. Kieokaew ◽  
B. Lavraud ◽  
N. Fargette ◽  
A. Marchaudon ◽  
V. Génot ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Field Conditions ◽  
Statistical Relationship ◽  
Transfer Event ◽  
Flux Ropes ◽  
Flux Transfer

scholarly journals Simultaneous observations of magnetopause flux transfer events and of their associated signatures at ionospheric altitudes

2004 ◽  
Vol 22 (6) ◽  
pp. 2181-2199 ◽  
Author(s):  
K. A. McWilliams ◽  
G. J. Sofko ◽  
T. K. Yeoman ◽  
S. E. Milan ◽  
D. G. Sibeck ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Southern Hemisphere ◽  
High Latitude ◽  
Field Conditions ◽  
Transfer Event ◽  
Flux Transfer Events ◽  
Subsolar Point ◽  
Reconnection Site ◽  
Flux Transfer

Abstract. An extensive variety of instruments, including Geotail, DMSP F11, SuperDARN, and IMP-8, were monitoring the dayside magnetosphere and ionosphere between 14:00 and 18:00 UT on 18 January 1999. The location of the instruments provided an excellent opportunity to study in detail the direct coupling between the solar wind, the magnetosphere, and the ionosphere. Flux transfer events were observed by Geotail near the magnetopause in the dawn side magnetosheath at about 4 magnetic local time during exclusively northward interplanetary magnetic field conditions. Excellent coverage of the entire dayside high-latitude ionosphere was achieved by the Northern Hemisphere SuperDARN radars. On the large scale, temporally and spatially, the dayside magnetosphere convection remained directly driven by the interplanetary magnetic field, despite the highly variable interplanetary magnetic field conditions, including long periods of northward field. The SuperDARN radars in the dawn sector also measured small-scale temporally varying convection velocities, which are indicative of flux transfer event activity, in the vicinity of the magnetic footprint of Geotail. DMSP F11 in the Southern Hemisphere measured typical cusp precipitation simultaneously with and magnetically conjugate to a single flux transfer event signature detected by Geotail. A study of the characteristics of the DMSP ion spectrogram revealed that the source plasma from the reconnection site originated downstream of the subsolar point. Detailed analyses of locally optimised coordinate systems for individual flux transfer events at Geotail are consistent with a series of flux tubes protruding from the magnetopause, and originating from a high-latitude reconnection site in the Southern Hemisphere. This high-latitude reconnection site agrees with plasma injected away from the subsolar point. This is the first simultaneous and independent determination from ionospheric and space-based data of the location of magnetic reconnection.

Dayside Magnetopause Reconnection and Flux Transfer Events: BepiColombo Earth-Flyby

2021 ◽  
Author(s):  
Wei-Jie Sun ◽  
James Slavin ◽  
Rumi Nakamura ◽  
Daniel Heyner ◽  
Johannes Mieth
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
European Space Agency ◽  
Flux Rope ◽  
Transfer Event ◽  
Flux Transfer Events ◽  
Space Agency ◽  
Flux Ropes ◽  
Flux Transfer ◽  
Magnetospheric Multiscale Mission

<p>BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury. The BepiColombo mission consists of two spacecraft, which are the Mercury Planetary Orbiter (MPO) and Mercury Magnetospheric Orbiter (Mio). The mission made its first planetary flyby, which is the only Earth flyby, on 10 April 2020, during which several instruments collected measurements. In this study, we analyze MPO magnetometer (MAG) observations of Flux Transfer Events (FTEs) in the magnetosheath and the structure of the subsolar magnetopause near the  flow stagnation point. The magnetosheath plasma beta was high with a value of ~ 8 and the interplanetary magnetic field (IMF) was southward with a clock angle that decreased from ~ 100 degrees to ~ 150 degrees.  As the draped IMF became increasingly southward several of the flux transfer event (FTE)-type flux ropes were observed. These FTEs traveled southward indicating that the magnetopause X-line was located northward of the spacecraft, which is consistent with a dawnward tilt of the IMF. Most of the FTE-type flux ropes were in ion-scale, <10 s duration, suggesting that they were newly formed. Only one large-scale FTE-type flux rope, ~ 20 s, was observed. It was made up of two successive bipolar signatures in the normal magnetic field component, which is evidence of coalescence at a secondary reconnection site. Further analysis demonstrated that the dimensionless reconnection rate of the re-reconnection associated with the coalescence site was ~ 0.14. While this investigation was limited to the MPO MAG observations, it strongly supports a key feature of dayside reconnection discovered in the Magnetospheric Multiscale mission, the growth of FTE-type flux ropes through coalescence at secondary reconnection sites.</p>

scholarly journals Two-dimensional electric field measurements in the ionospheric footprint of a flux transfer event

2000 ◽  
Vol 18 (12) ◽  
pp. 1584-1598 ◽  
Author(s):  
K. A. McWilliams ◽  
T. K. Yeoman ◽  
S. W. H. Cowley
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Flux Tube ◽  
Convection Velocity ◽  
Hf Radar ◽  
Two Dimensional ◽  
Plasma Convection ◽  
Transfer Event ◽  
Ionospheric Convection ◽  
Flux Transfer

Abstract. Line-of-sight Doppler velocities from the SuperDARN CUTLASS HF radar pair have been combined to produce the first two-dimensional vector measurements of the convection pattern throughout the ionospheric footprint of a flux transfer event (a pulsed ionospheric flow, or PIF). Very stable and moderate interplanetary magnetic field conditions, along with a preceding prolonged period of northward interplanetary magnetic field, allow a detailed study of the spatial and the temporal evolution of the ionospheric response to magnetic reconnection. The flux tube footprint is tracked for half an hour across six hours of local time in the auroral zone, from magnetic local noon to dusk. The motion of the footprint of the newly reconnected flux tube is compared with the ionospheric convection velocity. Two primary intervals in the PIF's evolution have been determined. For the first half of its lifetime in the radar field of view the phase speed of the PIF is highly variable and the mean speed is nearly twice the ionospheric convection speed. For the final half of its lifetime the phase velocity becomes much less variable and slows down to the ionospheric convection velocity. The evolution of the flux tube in the magnetosphere has been studied using magnetic field, magnetopause and magnetosheath models. The data are consistent with an interval of azimuthally propagating magnetopause reconnection, in a manner consonant with a peeling of magnetic flux from the magnetopause, followed by an interval of anti-sunward convection of reconnected flux tubes.Key words: Magnetospheric physics (magnetosphere · ionosphere interactions; plasma convection; solar wind · magnetosphere interactions)

scholarly journals Cluster observations of continuous reconnection at the magnetopause under steady interplanetary magnetic field conditions

2004 ◽  
Vol 22 (7) ◽  
pp. 2355-2367 ◽  
Author(s):  
T. D. Phan ◽  
M. W. Dunlop ◽  
G. Paschmann ◽  
B. Klecker ◽  
J. M. Bosqued ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
High Speed ◽  
Flow Speed ◽  
Plasma Jets ◽  
Current Layer ◽  
Magnetic Shear ◽  
Opposite Hemisphere ◽  
Entire Interval ◽  
Transfer Event

Abstract. On 26 January 2001, the Cluster spacecraft detected high-speed plasma jets at multiple crossings of the high-latitude duskside magnetopause (MP) and boundary layer (BL) over a period of more than 2h. The 4 spacecraft combined spent more than half of this time in the MP/BL and jets were observed whenever a spacecraft was in the MP. These observations were made under steady southward and dawnward interplanetary magnetic field (IMF) conditions. The magnetic shear across the local MP was ~100° and β~1 in the adjacent magnetosheath. The jet velocity is in remarkable agreement with reconnection prediction throughout the entire interval, except for one crossing that had no ion measurements inside the current layer. The flow speed measured in the deHoffmann Teller frame is 90% of the Alfvén speed on average for the 10 complete MP current layer crossings that are resolved by the ion measurements. These findings strongly suggest that reconnection was continuously active for more than two hours. The jets were directed persistently in the same northward and anti-sunward direction, implying that the X-line was always below the spacecraft. This feature is inconsistent with patchy and random reconnection or convecting multiple X-lines. The majority of MP/BL crossings in this two-hour interval were partial crossings, implying that they are caused by bulges sliding along the MP, not by inward-outward motion of a uniformly thin MP/BL. The presence of the bulges suggests that, although reconnection is continuously active under steady IMF conditions, its rate may be modulated. The present investigation also reveals that (1) the predicted ion D-shaped distributions are absent in all reconnection jets on this day, (2) the electric field fluctuations are larger in the reconnecting MP than in the magnetosheath proper, but their amplitudes never exceed 20mV/m, (3) the ion-electron differential motion is ~20km/s for the observed MP current density of ~50nA/m2 (∇× B), thus inconsequential for the deHoffmann-Teller and Walén analyses, (4) flows in an isolated flux transfer event (FTE) are directed in the same direction as the MP jets and satisfy the Walén relation, suggesting that this FTE is also generated by reconnection. Finally, the present event cannot be used to evaluate the validity of component or anti-parallel merging models because, although the magnetic shear at the local MP was ~100°(≪180°), the X-line may be located more than 9RE away (in the opposite hemisphere), where the shear could be substantially different.

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